Article for separating spot welded panels



Sept. 24, 1963 3,104,564

E. D. HOUGEN ARTICLE FOR SEPARATING SPOT WELDED PANELS Filed Dec. 5,1960 22 I I a. 6 32 33a. "H 74%,,

S FIG a INVENTOR.

-v EVERETT D. HOUGEN M v' M ATTORNEYS United States Patent 3,104,564ARTICLE FOR SEPARATING SPOT WELDED PANE This invention relates generallyto metal-working tools, and more particularly to a rotary cutting toolfor disconnecting metallic members which are originally joined togetherby one or more spot welds.

In the art of repairing and refinishing collision damaged sheet metalparts of automotive vehicles, such as the body panels and fendersthereof, it is often necessary to remove the damaged panel from thevehicle in order to straighten or otherwise recondition the same. Whenthe s'heet metal panels are joined together by spot welds, the damagedpanel has hitherto been separated from the undamaged panel either bydrilling a hole of sufiicient diameter through both panels so that theentire spot welded port-ions of the panels are removed, or by splittingthe spot-welded seam apart by driving a thin sharp chisel between thetwo panels.

Both methods have disadvantages. In the former, it is necessary tocenter punch the spot weld in order to properly position and start thedrill in true position. Drilling out the entire spot welded portions ofboth panels consumes excessive time and power, and it is practicallyimpossible to make overlapping drillings when two spot Welds are locatedclose together. Moreover, in rejoining the repaired panel to theundamaged panel, the presence of holes in both of these panels requiresthe use of sophisticated, high temperature welding tools and techniquesoften unavailable in the average body shop. In the chisel method ofseparating the panels, the undamaged as well as damaged panels are oftendistorted and bent, adding to the labor and cost involved in making therepair.

Accordingly, it is an object of the present invention to provide arotary cutting tool for separating two metallic members joined by a spotweld by a method in which a minimum of metal is removed withoutdistorting the members, thereby reducing the time, power and expenserequired to effect the separation.

Another object is to provide an improved tool for quickly cutting apartsheet metal panels that are spot welded together and which enables thepanels to be rejoined in a manner which facilitates accuratere-alignment of the members during re-asseinbly thereof and enables theuse of low temperature rewelding or brazing tools and techniquesavailable at low cost and easily mastered by body shop personnel.

A further object is to provide an improved self-centen ing rotary toolof the tubular saw type for removing a minimum of metal when separatingtwo spot welded panels, which tool is simple in construction and whichmay be easily adjusted to out to any predetermined depth within therange of adjustment of the tool.

In the accompanying drawing:

FIG. 1 is a perspective view of the rotary cutting tool of the inventionreceived in a suitable chuck;

FIG. 2 is a longitudinal section of the rotary cutting tool taken online 2--2 of FIG. 1;

FIG. 3 is a fragmentary elevational view, partially in 3,104,564Patented Sept. 24, 1963 ice section, illustrating the step of separatingtwo panels spot welded together by utilizing the tool of the invention;

FIG. 4 is a fragmentary elevational view partially in sectionillustrating the completion of the step shown in FIG. 3;

FIG. 5 is a fragmentary sectional view of the panels disconnected fromone another and with the tool removed;

FIG. 6 is a fragmentary elevational view of a portion of the overlappingspot welded seam along which the panels are joined together, withencircling grooves cut around two of the spot welds thereof;

FIG. 7 is a fragmentary elevational view in section of the two panel-sre-assembled;

FIG. 8 is a fragmentary elevational view of a modification of the toolof the invention illustrating its use as a hole cutter.

T he rotary cutting tool 10 of the invention (FIGS. 1 and 2) includes acylindrical body or arbor 11 which is adapted to be received in suitabletool holding means of a rotary power supplying device, such as a chuck Cof an electric hand drill, not otherwise shown. The forward end portionof arbor 11 is provided rm'th external threads 12 which mate withinternal threads 14 of a double-ended cylindrical cutter blade 16removably received on the end of the arbor.

Cutter blade 16 is made in the form of a sleeve with a plurality ofcutting teeth 17 and 18 formed in the respective peripheral end edgesthereof. Cutting teeth 17 and 18 are shaped for high speed metal cuttingin accordance with known design, but are reversed with respect to oneanother so that cutter blade 16 is reversible, thus permitting cuttingteeth 18 to be used after cutting teeth 17 have become dulled from use.The central portion of cutter blade 16 is provided with an integralflange 19 which provides radial shoulders 19a and 19b spaced axiallyinward from cutting teeth 17 and 18 respectively, this spacing beingdetermined by the maximum penetration for which the cutter blade 19 isdesigned.

Arbor 11 has (an axial bore 21 formed in the forward portion thereofwhich opens into a counterbore 22 coaxial with bore 21, providing ashoulder 23 therebetween. A pilot rod 24 having a conical point 26 atthe forward end thereof made of high speed steel is received with aclose sliding lit in bore 21 for centering the rotary cutting tool overthe portion of the material to be cut. The rear end of rod 24 is upsetto form an enlarged portion 27 which abuts shoulder 23 to limit forwardtravel of pilot rod 24.

Pilot rod 24 is urged to a fully extended position (FIG. 2) by means ofa resilient member comprising helical compression spring 28 slidablyreceived in countterbore 22. The rear end of spring 28 abuts anexternally threaded plug 29 threadably received in internal threads 31provided at the rear of counterbore 22. Plug 29 is provided with atransverse slot 29a adapted to receive a screw driver for use in axiallyadjusting the plug. A bearing ball 32 rides with a rolling, sliding fitin counterbore 22 between the forward end of spring 28 and enlargedportion 27 of pilot rod 24 to form an anti-friction seat therefor.Real-ward travel of bearing ball 32, and hence pilot rod 24, ispositively limited by the provision of a spacer rod 33 slidably receivedwithin spring 28. Spacer rod 33 is cut to a predetermined length so that4 the conical point 26 of pilot rod 24 may retract flush with theforward end of arbor 11 (dotted line showing, FIG. 2.).

If desired the axial position of spacer rod 3-3 may be indicated by aprojecting portion 33a on the forward end of spacer rod 33. Projection33a extends perpendicularly from rod 33 through the space betweenadjacent convolutions of spring 28 and through an axial slot 11a formedin the side of arbor 11. Suitable graduations 11b are marked or scribedon the outer surface of arbor 11 along the longitudinal edges of slot11a to form a depth gauge useful in indicating the axial distance whichpilot rod 26 can move during retraction thereof before it is stopped byhearing ball 32 bottoming against rod 33 and the latterbottoming againstplug 29.

A modified form of depth gauge is shown in FIG. 8. In this embodimentthere is no projection provided on spacer rod 33 and arbor 11 need notbe slotted. Instead, a gauge plug 36 is provided in lieu of plug 29.Plug 36 has an externally threaded portion 37 adapted to be received inthe internal threads 31 of counterbore 22. Integral with threadedportion 37 and extending rearwardly therefrom is an unthreadedcylindrical portion 38 which projects beyond the end of arbor 11 andterminates with a screw driver slot 39. Suitable graduation-s 41 areprovided on the outer surface of portion 38 to visibly indicate theaxial position of plug 35.

To set the depth of penetration of cutting teeth 17, either form of tool16 is brought up against the surface of the portion of the work to becut so that point 26 of pilot rod 24 is retracted flush with the leadingedges of cutting teeth 17. Plugs 29 or 36 are then screwed axially intoarbor 11 until pilot rod 24, bearing ball 32 and spacer rod 33 abut oneanother. Plugs 29 or 36 are then rotated in the reverse direction tomove the same axially rearward a distance equal to the depth of cutdesired. This distance is easily read by observing the registry ofgraduations 11!) with projection 33a, or of graduations 41 with respectto the rear face of arbor 11. Of course, cutting tool may be constructedwithout depth gauging structures such as projection 33a and extension38, in which case the depth of penetration may be set rather accuratelyby observing the axial position of plug 29 and performing one or twotest cuts, depending upon the skill of the operator.

The operation of rotary cutting tool 10 will become more apparent in thefollowing description of the method of the invention for disconnectingand rejoining two metallic members spot welded together. Referring firstto FIG. 3, a pair of sheet metal panels 42 and 43 are shown joinedtogether by a spot welded portion 44 thereof. The thickness of the panelto be removed is determined, and the screw plug 29 of the rotary cuttingtool 10 is adjusted to penetrate at least all the Way through thispanel. With tool 10 thus adjusted it is brought perpendicular to thesurface of panel 43 with the conical point 26 against the center, of thespot welded portion 44. Tool 10 is then pushed lightly against thepanel, causing the pilot rod 24 to retract against the force of spring28 until cutting teeth 17 contact panel 43. Due

to the anti-friction bearing ball 32, pilot rod 24 is free to remainfixed against rotation when rotary motion is imparted to the cuttingtool simultaneously with the application of the cutting teeth to thepanel.

As shown in FIGS. 4-6, upon application of moderate pressure cuttingteeth 17 penetrate panel 43 (and preferably a short distance into panel42), cutting an annular groove 45 around the periphery of the spotwelded portion 44 of the panels. Further penetration of cutting teeth 17is prevented by pilot rod 26, since further retraction of the pilot rodis prevented by the abutment of the rear face of enlarged portion 27against bearing ball 32, which in turn, is held against further axialmovement by spacer rod 33 bottoming on the forward face of plug 29'.

After the cut is completed, the rotary cutting tool is Withdrawn'andpanels 42, 43 separated from one another, as shown in FIG. 5. A circularhole 43a is formed in outer panel 43, while the spot welded portion ofpanel 43 which remained in the center of the annular cut forms acylindrical projection 43b on the surface of inner panel 42 since it isstill welded thereto. Separation of the panels is made possible by thecircular cut around the spot welded portion 44, since the panels arejoined together only at the spot welded portion and not at otheradjacent portions of the overlapping seam. It is to be understood thatthe outside diameter of cutter blade 16 measured at cutting teeth 17must be equal to or larger than the diameter of the spot welded portion44 to effect separation of the panels. It has been found preferable touse a rotary cutting tool having an arbor of one quarter inches outsidediameter so as to fit the quarter inch electric drill found in most bodyshops, and having a cutter blade with an outside diameter of 4 inch soas to encircle most spot welds found on present day cars and trucks.However, if a variation in the diameter of spot welds is encountered, itis a simple matter to change to a cutter blade with a diameter largeenough to encircle the spot weld.

After the disconnected panels have been straightened or otherwisereconditioned they may be easily re-assembled in accordance with furthersteps in the method of the invention. As shown in FIG. 7, panels 42 and43 are re-aligned with one another in the original connected arrangementthereof merely by relocating projection 43b in hole 43a. After all theprojections are thus centered in the respective holes from which theywere cut, the panels are temporarily held together by a clamp or othersuitable means. Low temperature tools (welding or brazing) are then usedto heat the panels around the groove 45 and low melting point weldingmetal 46 is puddled therein to fuse with and form a bond between theside walls of hole 43a, the surfaces of projection 43b and the bottom ofthe groove. The freshly cut annular groove 45 simplifies the reweldingof the panels since it pro: vides a well for the molten metal andfurnishes a clean, bright metal area for a high strength, lowtemperature bond.

The rotary cutting tool 10 of the invention is alsouseful in cuttingstraight-through holes in metal, such use being shown in FIG. 8. Forthis type of work, pilot rod 24 is adjusted for full retraction (flushwith the forward end face of arbor 1 1) to permit maximum penetration ofcutter blade 16. After the combined thicknesses of the panels 43 and 42are penetrated, the point 26 will forcibly expel the disk-like portion47 cut from the panels. Further penetration of cutter blade 16 isprevented by shoulder 19a of flange 19 abutting the face of panel 43, afeature contributing to the ease with which the tool may be withdrawnfrom the straight-through hole at the completion of the cut. The tool isnormally used in this fashion as a conventional hole saw when it isdesired to replace the outer panel 43 with a new panel. The hole cutthrough the inner panel 42 provides a freshly out well so that weldingmetal may be more easily applied from the inside ofthe panels.

Of course, the rotary cutting tool 10 is useful as an By axiallyadjusting threaded plug 29' the tension of, spring 28 can be set toproduce heavy or light pressure? ordinary hole cutter in otherapplications, and in all applications it eliminates the need for centerpunching due to the provision of the spring loaded pilot rod 24.

on pilot rod 24 for hole cutting in thick or thin metal re- '1spectively.

drills tend to slip or skate off the panel: The pilot rod also permitsoverlapping cuts to be easily made with the tool when, for instance, thespot welds are located close together. Less metal is removed when thetubular saw type metal cutter 16 is used instead of a drill, thushastening the disassembly of spot welded panels. Moreover, in theoperation of the tool and in the method of the invention, the cuttingoccurs in the softest portion of the panels thereby contributingmaterially to the speed of the operation and the life of the tool. Thisis due to the fact that the metal in the area of the annular cut hasbeen annealed by the heat generated during spot welding, whereas thesurrounding metal remained in its work hardened state while that of thespot welded portion was rehardened by being subjected to more rapidcooling due to the presence of the water-cooled copper electrodes. Inaddition, by using the method of the invention the panels are notnicked, bent or otherwise damaged as so often occurs when a chisel typetool is used to separate the panels.

I claim:

1. A cutting tool adapted to be received in the tool holding means of arotary power supplying device for rotation thereby for disconnectingspot welded metal members, including in combination, an arbor having anaxial bore extending from one end thereof and a co-axial counterbcreextending from the other end thereof providing a shoulder therebetween,a pilot rod slidably received in said axial bore of said arbor andhaving a pointed forward end portion projecting beyond said one end ofsaid arbor for engaging a spot welded portion of the metal members tocenter the cutting tool thereon, said pilot rod having an enlargedportion disposed within said counterbore for engaging said shoulder tolimit forward sliding movement of said pilot rod, cutting meanssupported on said arbor at said one end thereof for rotation therewith,said cutting means having a hollow cylindrical portion extending beyondsaid one end of said arbor with a plurality of cutting teeth formed inthe peripheral leading edge of said cylindrical portion for removing aring of metal from around the spot welded portion of the members,resilient means supported within said counterbore between said pilot rod'and said other end of said arbor for urging said forward end portion ofsaid pilot rod beyond said teeth for initially centering the cuttingtool, depth stop means disposed within said hollow arbor for positivelylimiting the retraction of said pilot rod so that said cutting meanspenetrates to a predetermined maximum depth beneath the surface of themetal, said resilient means comprising a helical compression spring, andsaid depth stop means including a screw plug threadably received foraxial adjustment in said counterbore and against which one end of saidspring seats, a bearing ball received in said counterbore with a closerotatable fit between the other end of said spring and the rearward endof said pilot rod to form an antifriction abutment there/betweenpermitting relative rotation therebetween, and a rigid stop rod havingan axial dimension and diameter less than that .of said spring and beingreceived for axial sliding movement therein so that said bearing ballbottoms against said stop rod to limit retractile movement of said pilotrod in accordance with the axial adjustment of said screw plug.

2. The combination as set forth in claim 1 wherein said screw plugincludes an externally threaded portion threadably receivable for axialadjustment in said counterbore and an unthreaded portion extendingbeyond said other end of said arbor and having graduations thereon forvisibly indicating the axial position of said screw plug with respect tosaid other end of said arbor.

3. A tubular saw comprising a cylindrical shank having one endexternally threaded and its opposite end internally threaded, said shankhaving an axial through bore therein which is ensmalled at theexternally threaded end of the shank, a cylindrical saw blade threadedover the externally threaded end of the shank, a pilot rod extendingaxially through the ensmalled portion of the bore and having an enlargedend within the larger bore portion to limit the extent to which theouter end of the pilot rod extends axially outward beyond the free endof the saw blade, a plug threaded into the internally threaded end ofthe shank for adjustment within said bore toward and away from theopposite ends of the shank and a compression spring acting between saidplug and the enlarged end of the pilot rod and yieldably urging thepilot rod axially outwardly of the bore, said cylindrical saw bladehaving axially extending cutting teeth at the free end thereof andhaving a radially enlarged shoulder around its outer periphery spacedaxially from the cutting teeth, a stop rod extending axially within saidspring, said rod having a length 'less than the axial distance betweensaid plug and the enlarged end of the pilot rod and having one endnormally spaced from the plug so that the pilot rod is capable ofretracting into said bore against the bias of said spring until suchretracting movement is arrested by the stop rod engaging the plug tothereby form an axially solid connection between the plug and the pilotrod, the extent of retraction of the pilot rod being variable inaccordance with the axial adjustment of said plug at the internallythreaded end of said shank.

4. The combination called for in claim 3 including a bearing ballinterposed between the adjacent ends of the pilot rod and the stop rodand forming an anti-friction axial driving connection therebetween whichpermits relative rotation between the pilot rod and the stop rod.

5. A circular hole saw adapted for mounting on the end of a threadedsupport-ing shank comprising a cylindrical tubular element having anaxial through bore, said bore being ensmalled at the central portion ofthe tubular ele ment and forming radially inwardly projecting annularshoulders spaced axially inwardly from the opposite extremities of thetubular member, said central portion being internally threadedformounting on the threaded end of a supporting shank and the tubularmember being formed with a plurality of axially extending saw teeth atthe axially opposite extremities thereof.

6. A circular hole saw as called for in claim 5 wherein said tubularmember is formed with a radially enlarged portion around the outerperiphery thereof, said radially enlarged portion being locatedintermediate the axial opposite extremities of the tubular member toform a circumferentially extend-ing shoulder spaced axially inwardlyfrom each end of the tubular member to thereby provide a stop forlimiting the maximum penetration of the teeth into the material beingcut.

7. A tubular saw comprising a cylindrical shank having one endexternally threaded and its opposite end internally threaded, said shankhaving an axial through bore therein which is ensmalled at theexternally threaded end of the shank, Ia cylindrical saw blade threadedover the externally threaded end of the shank, a pilot rod extendingaxially through the ensmalled portion of the bore and having an enlargedend within the larger bore portion to limit the extent to which theouter end of the pilot rod extends axially outward beyond the free endof the saw blade, a plug threaded into the internally threaded end ofthe shank for adjustment within said bore toward and away from theopposite ends of the shank and a compression spring acting between saidplug and the enlarged end of the pilot rod and yieldably urging thepilot rod axially outwardly of the ibore, said cylindrical saw bladehaving axially extending cutting teeth at the free end thereof andhaving a radially enlarged shoulder around its outer periphery spacedaxially from the cutting teeth, said saw blade being of tubular form,the blade having an internally threaded portion intermediate its endswhich is threadedly engaged with the externally threaded end of theshank, said intermediate portion of the saw blade having a smaller innerdiameter than the remainder of the blade and forming an annular shouldertherein, the external-ly threaded end of the shank defining a shoulderon the shank engageable with the annular shoulder within the blade whenthe blade is threaded on the shank.

8. A tubular saw comprising a cylindrical shank having one endexternally threaded, the externally threaded end of the shank having adiameter smaller than the adjacent portion of the shank t0 define ashoulder, a tubular saw blade, said blade having an internally threadedportion intermediate its ends which is threadedly engaged with 5 theexternally threaded end of the shank, said intermediate portion of thesaw blade having a smaller inner diameter than the remainder of theblade and forming an annular shoulder therein which engages saidshoulder adjacent the threaded end of the shank, said blade having 10axially extending cutting teeth at both ends thereof.

References Cited in the file of this patent UNITED STATES PATENTSDa-Izell Dec. 26, 1899 Bennett Apr. 9, 1912 Rairden Nov. 22, 1927Schreiner July 3, 1928 Leach June 28, 1955 Rowley Sept. 23, 1958 FOREIGNPATENTS France May 26, 1947

1. A CUTTING TOOL ADAPTED TO BE RECEIVED IN THE TOOL HOLDING MEANS OF AROTARY POWER SUPPLYING DEVICE FOR ROTATION THEREBY FOR DISCONNECTINGSPOT WELDED METAL MEMBERS, INCLUDING IN COMBINATION, AN ARBOR HAVING ANAXIAL BORE EXTENDING FROM ONE END THEREOF AND A CO-AXIAL COUNTERBOREEXTENDING FROM THE OTHER END THEREOF PROVIDING A SHOULDER THEREBETWEEN,A PILOT ROD SLIDABLY RECEIVED IN SAID AXIAL BORE OF SAID ARBOR ANDHAVING A POINTED FORWARD END PORTION PROJECTING BEYOND SAID ONE END OFSAID ARBOR FOR ENGAGING A SPOT WELDED PORTION OF THE METAL MEMBERS TOCENTER THE CUTTING TOOL THEREON, SAID PILOT ROD HAVING AN ENLARGEDPORTION DISPOSED WITHIN SAID COUNTERBORE FOR ENGAGING SAID SHOULDER TOLIMIT FORWARD SLIDING MOVEMENT OF SAID PILOT ROD, CUTTING MEANSSUPPORTED ON SAID ARBOR AT SAID ONE END THEREOF FOR ROTATION THEREWITH,SAID CUTTING MEANS HAVING A HOLLOW CYLINDRICAL PORTION EXTENDING BEYONDSAID ONE END OF SAID ARBOR WITH A PLURALITY OF CUTTING TEETH FORMED INTHE PERIPHERAL LEADING EDGE OF SAID CYLINDRICAL PORTION FOR REMOVING ARING OF METAL FROM AROUND THE SPOT WELDED PORTION OF THE MEMBERS,RESILIENT MEANS SUPPORTED WITHIN SAID COUNTERBORE BETWEEN SAID PILOT RODAND SAID OTHER END OF SAID ARBOR FOR URGING SAID FORWARD END PORTION OFSAID PILOT ROD BEYOND SAID TEETH FOR INITIALLY CENTERING THE CUTTINGTOOL, DEPTH STOP MEANS DISPOSED WITHIN SAID HOLLOW ARBOR FOR POSITIVELYLIMITING THE RETRACTION OF SAID PILOT ROD SO THAT SAID CUTTING MEANSPENETRATES TO A PREDETERMINED MAXIMUM DEPTH BENEATH THE SURFACE OF THEMETAL, SAID RESILIENT MEANS COMPRISING A HELICAL COMPRESSION SPRING, ANDSAID DEPTH STOP MEANS INCLUDING A SCREW PLUG THREADABLY RECEIVED FORAXIAL ADJUSTMENT IN SAID COUNTERBORE AND AGAINST WHICH ONE END OF SAIDSPRING SEATS, A BEARING BALL RECEIVED IN SAID COUNTERBORE WITH A CLOSEROTATABLE FIT BETWEEN THE OTHER END OF SAID SPRING AND THE REARWARD ENDOF SAID PILOT ROD TO FORM AN ANTIFRICTION ABUTMENT THEREBETWEENPERMITTING RELATIVE ROTATION THEREBETWEEN, AND A RIGID STOP ROD HAVINGAN AXIAL DIMENSION AND DIAMETER LESS THAN THAT OF SAID SPRING AND BEINGRECEIVED FOR AXIAL SLIDING MOVEMENT THEREIN SO THAT SAID BEARING BALLBOTTOMS AGAINST SAID STOP ROD TO LIMIT RETRACTILE MOVEMENT OF SAID PILOTROD IN ACCORDANCE WITH THE AXIAL ADJUSTMENT OF SAID SCREW PLUG.